SYSTEM AND APPARATUS FOR THE CONVERSION OF VIDEO SIGNALS INTO IMAGES ON A LIGHT-RESPONSIVE RECORDING SURFACE

摘要

Gamma (or other linearity) correction in an imaging system which provides photographic reproductions of images represented by video signals is achieved by controlling the duration of exposure of a constant intensity scanning beam. A moving threshold signal is swept at a varying rate corresponding to a gamma correction curve between opposite limits over a given total exposure interval, as the image is repeatedly presented. The instantaneous amplitude of the video signal is compared to threshold signal and the results of the comparison used to control whether the beam is on or off for a given picture area. The gamma correction curves are advantageously presented as numerical sequences defining interlinked incremental segments of different slope.